(1) Field of the Invention
This invention relates to a conveyor belt, and more particularly to an improvement in a conveyor belt adapted to perform conveyance while being elastically deformed in such a cylindrical shape as to overlap both widthwise edge portions thereof with each other.
(2) Description of the Prior Art
As the conveyor belt of this type, there has been hitherto been used a belt as shown in FIG. 1. In this case, the belt 1 is constituted by upper and lower covering rubber layers 2 and 3 and a core layer 4 embedded therebetween.
As shown in a plan view of FIG. 2, the conveyor belt 1 is trained about a pulley 5 and is gradually deformed elastically in a cylindrical shape while being run from the pulley up to a belt-deforming roller 6 consisting, for instance, of six roll segments, which is arranged at a predetermined distance apart from the pulley.
As shown in an enlarged sectional view of FIG. 3, when the conveyor belt 1 reaches the belt-deforming roller 6, it is elastically deformed in such a cylindrical shape that the widthwise edge portions of the belt overlap with each other at a angle .alpha. of an overlap portion 7 of about 60.degree., by means of the six roll segments constituting the roller 6 and being disposed in a plane perpendicular to the belt-running direction. Such an elastically deformed shape of the conveyor belt is maintained by the action of a plurality of deformation-holding rollers 6 arranged at a predetermined interval in the belt-running direction until the material to be conveyed reaches a predetermined discharge position.
Moreover, the material to be conveyed such as powder materials, granular materials or the like is supplied onto the conveyor belt 1 between the pulley 5 and the belt-deforming roller 6 during the running of the belt.
However, according to such a prior art, the widthwise edge portions of the conveyor belt 1 are brought into rubber-contact with each other at the overlap portion 7, so that the frictional resistance between the upper and lower covering rubber layers 2, 3 at the overlap portion 7 is large. Therefore, large power is particularly required for elastically deforming the conveyor belt 1 in the cylindrical shape between the pulley 5 and the belt-deforming roller 6 or for squeezing the conveyor belt 1 swelled in a barrel-like shape between the two rollers 6, 6' as shown in FIG. 2 into the original cylindrical shape. In the worst case, a problem is created that the frictional resistance leading to the running resistance of the conveyer belt 1 grows up to about one third of the total running resistance.